The regulation of hormone production in normal and neoplastic human pituitary gland tissues will be investigated using morphological, immunohistochemical and biochemical methods. Morphological studies at the light and electron microscope level and immunohistochemical methods with antibodies against pituitary hormones and chromogranin will be used to characterize normal pituitaries, prolactin (PRL) and null cell (undifferentiated) adenomas. The effects of estrogens, bromocriptine, thyrotropin releasing hormone, gonadotropin releasing hormone, arachidonic acid and phorbol esters on PRL release and on dopamine receptor binding will be studied in vitro and by ultrastructural immunohistochemistry. The regulation of the biosynthesis of PRL messenger RNA in culture pituitary cells will be examined by in situ hybridization using synthetic oligonucleotide probes. The reverse hemolytic plaque assay which detects hormone production by single cells will be used to study the production of PRL and growth hormone (GH) by the same normal and neoplastic pituitary cells. Preliminary studies have shown that cultured PRL-producing adenoma cells respond to various secretagogues in our culture system and that these tumors are often producing both PRL and GH as detected by the reverse hemolytic plaque assay, although the usual immunohistochemical methods often fail to detect both PRL and GH production in the same tumor. Significant levels of dopamine receptor binding have been detected in four normal pituitaries which have been examined within 3 hours post mortem. We have shown that most null cell adenomas can be characterized immunohistochemically by immunoreactivity with a monoclonal antibody against chromogranin which was developed in our laboratory. This proposal is designed to understand the morphological and biochemical differences and similarities betwen normal and neoplastic human pituitary tissues and to gain more insight into the biology of normal and neoplastic pituitary cells.